LC-EC of Endorphins

Abstract

Reversed phase liquid chromatography with electrochemical detection (LC-EC) was used to separate a series of endorphin standards. Chromatographic conditions were manipulated so that methionine- and leucine-enkephalin were clearly resolved from other endorphins of similar hydrophobicity using an isocratic mobile phase. The most significant factors affecting endorphin retention were the concentration and type of organic modifier in the isocratic mobile phase. Hydrodynamic voltammograms were performed for methionine- and leucine-enkephalin to assess their electroactivity. Both enkephalins were oxidized with a glassy carbon electrode only at high potentials (>+.90V vs Ag/AgCl). The effect of these high potentials on the sensitivity of electrochemical detection of endorphins was evaluated.